The present invention relates to an internally cooled mandrel for rolling mills of pipes of relatively large wall thickness, and more particularly, the invention relates to a mandrel for use in Pilger type rolling mills.
A mandrel of the type to which the invention refers is, for example, disclosed in French Pat. No. 1,272,096. It was found that these known mandrels pose difficulties if used in conjunction with rolling thick-walled hollows. German printed patent application No. 2,331,989 discloses building up of hard-facing sleeves on a mandrel to be used for the rolling of hollows. These sleeves are plugs which match the surface of the mandrel locally to particular local loads. This cladding process employs highly alloyed materials.